Multistroke fluid operated power actuator



July 22, 1952 H. w. 'rREvAsKxs MULTISTROKE FLUID OPERATED POWER AcTUAfroR Filed Aug. 26. 1947 mf l Patented `uly 22, y 1952 MULTISTROKE FLUID OPERATED POWER v Y f ACTUATOR c Henry William Trevaskis, Solihull, Birmingham, c England, assig'nor to Dunlop Rubber Company Y Limited, London, England, a British corpora- 1 tion Application August 26, 1947, Serial No. 770,655 In Great Britain September 17, 1946 1 Myinvention relates to a'fluid operated jack of :thetype having a straight vthrough piston rod i.` e. a" piston rod projecting from each extremity ofthe cylinder. -v

' .Such a rod is provided with, for example, an aperture at each end forsecuring the rod ends to two members Such as lapson an aircraft and said rod actsl as a coupling member to effect simultaneous movement of themembers.

' It is an `object of the invention to provide a.

means of connectionbetween the piston and piston rodof a jack of this type whereby the piston is permitted to rock during its linear .travel along the cylinder to allow for any misalignment between the cylinder wall andthe piston rod.

According to this invention there is provided a iiuidj operated powerr actuator having a straight through piston rod wherein the piston is extended in the direction of the'axis of the cylinderto form abell-like structure and is mounted on'the piston rod in a rockable manner at one extremity and contacts the cylinder surface at the other extremity. 4 .Y A Preferably according to lthis invention the pi'ston is mounted onV the pistonrod. by a prtionparallel l.with the cylinder axis engaging a portion convex in a direction.longitudinally of the cylinder axis, said piston being loosely engaged betweenv abutments on the rod.

A multi-stroke power actuator or jack according to this invention havingV a straight through piston rod comprises ya main piston extended in the direction of the axis yof the cylinder to form a bell-like structure and mounted on the piston rod in a rockable manner atone extremity and contacting the 'cylindersu'rface at' the' other extremityrfa sleeve slidableupon the piston rod, a secondaryv piston adapted'toab'ut the main piston 'and extended 'in the'direction 'of the axis of the cylinder to 'form a be'll-likevstructure mounted v on lthe sleeve `in` a rockable ,manner at'one extremity and contacting vthe-cylinder surface at thefother extremity, stop' means to limit the stroke of the secondary piston', passage means inthe piston rod cornmunicatifigv 'with the cylinder between the two piston`s,"pa'ss age means communieating with the cylinder on the outer side of one 8 Claims. (C1. 121,-38)

Fig. 2 is a fragmentary longitudinal sectional view of a modification. f

Fig. 3 is a sectional detail, on a larger scale, oi elements of the power actuator and with the curvature of certain elements slightly exaggerated for purposes of illustration. l y

In Fig. 1 the piston rod I extends straight through the cylinder .Landat eachend has a connection 3 formed with an aperture 4 for securingthe rod to two members which are required to be simultaneouslymoved.v A main piston 5 is formed with a crowns and a side wall 1 which extends in thedirection of the axis of the cylinder to form a bell-like structure. The crown is formed with an aperture 8 thesurface of, which is of arcuate shape convex ina direction longitudinally of the cylinder axis and the piston base isformed with a ange 9 provided withrings I0, the periphery of said ange being of arcuate shape convex in a direction longitudinally of the cylinder axis. The crown engages a .parallel'portion Il of the piston rod and said crown is retained on said portion between a shoulder` yli anda nut I3 vin a manner which allows the piston to rock on the rod. A sealing ring VIll is housed within an annular groove in the aperture to contact the parallel portion of the piston rod.l l

A secondary piston` I5is formed with a crown I6 and a side wall I1 whichl extends'inthe direction of the axis of the cylinder to form a belllike structure. ,The crown is formed with an aperture I8 the surface of which is of 'arcuate shape convex in a direction longitudinally' of the cylinder axisand the piston base is formed with a flange I9'provided with rings 20. rIfhe periphery of said iiange is of convex arcuate shape in a directionlongitudinally ofthe-cylinder axis' as illustrated more particularly in Fig. 3. The crown VI 6 engages a parallel portion2l of'a sleeve 22 slidablylmounted on 'the piston rod land said crownv is retained on said'portion between aV shoulder 23 and a Vnut 24 vin a manner which allows the secondary piston torock on the sleeve. A sealing ring 25 is housed within an annular groove in the aperture I8 to contact the parallel portion of the sleeve. g L

The sleeve is slidably ,mounted ina vbearing 26 provided in ann end cap 2 1 -of the cylinder so that the piston rod is supported indirectlyby saidbearing 26 and alsov said rod is supported directly by a bearing 2B formed at theother end of the cylinder. Suitable sealing and lubricating rings 29 are located between the piston rod and cylinder and piston rod and sleeve, and sealing and lubricating .from the opposite side of secondary piston I5. The piston rod is formed with passages 33 and 3,4 and a nozzle 35 is secured in said rod to admitA fluid to and exhaust fluid fromK between the piston and I5. Considering theoperation ofthe jack fromzthe der having a narrow portion between said abut- Y ments and contacting said piston rod on a cirposition shown in Fig. 1 ofthe; drawings; admis-I Y sion of fluidV to the cylinderjl through nozzle 32V` traverses the secondary piston I 5V which, abutting against the piston 5 at 36 also traverses said piston 5 and the piston rod I by theY nut'. I3to`V an extenty limited by abutment of a nut 371on1the-- 'sleevei against a face 38 of the end cap 2l. Admission of fluid to the cylinder between the pistons through nozzle traverses thepiston 5 and piston rod to the extent limited by the end ofV the cylinder. By admission ofilud'to the cylinder through nozzle 3| and connection'of nozzles 32 and 35 vto exhaust means the. two pistons are returned to a position'in which the secondary pistonV I5 rests within the main piston 54 as shown in Fig. 1.

,Inpthe modification shownin Fig. 2j theV main pistoni has `a crown' formed with a parallel aperture 39 and said crown engagesthe piston rod I at a portionV 40 which is of arcuate shape 'convex in a direction longitudinally of the cylinder axis. The secondary piston. I5 has a crown "IS, formed with` a parallelaperture 4I and said crown engages the sleeve 22'at a portion 42 which isof'arcuate shape convex in a directionlongi- Vtudinally of the cylinder'axis. "glutei-natively, instead of.A the piston vbeing mounted ina rockable manner-on the piston rod or sleeve by means of Ya convex portion which is of arcuate shape; said convex portion may be formed tapered i. e. with plane iianks.- I

Insteadof the piston being retained between a nut anda shoulder it'may be retained between two nuts or by means known as Circlips.

Iteshoul'd be appreciated therefore that in a jack Vaccording to any of the constructions described the piston-will rock on the piston rod to allow for any misalignment between the cylinder andthe piston rod, and further it should be appreciated that the greater the distance between thepiston ycrown and base the lessrwill.V be Vthe disturbing or tilting effect onthepiston.

V`Having described my invention what I claimis: v1. A fluid` operated power actuator comprising acylinder, a pistonrod extending axially therethrough, a piston in said cylinder having an opening through which the piston rod extends, the surface of said opening being in full contact with said piston rod, one of the contacting surfaces of said opening and rod being arcuate in.longitudinal section, said piston extending longitudinally about said, rod and thencemoutwardly to contact with the wallrof the cylinder on a circumferential 1ine'of contact, the surface of said outwardlyY extending portion Vazljacent the cylin-v der wall diverging on opposite sides of said line of contact from the wall of said cylinder. Y 2. A fluid operated power actuator comprising a cylinder, a piston rod extending axiallythrough said cylinder and having'a pair ofspac'ed abutments within saidcylinder', a piston Vin said cylin- ,line of contact.

3. The actuator of claim 2 in which the surface of said piston in contact with said piston rod betweensaidabutments is arcuate in longitudinal section.

4. 'Ihe actuator of claim 2 in which said piston rod has a surface between said abutments which is arcuate in longitudinal section.

V5;' The actuator of claim 1 in which said piston is provided with a sealing ring at the line of contact with said cylinder.

6. A iluid operated power actuator comprising 'a cylinder, a piston rod extending axially through said cylinder, a main piston in said cylinder engaging said piston rod with a rocking engagement and extending longitudinally about said rod and thence outwardly to contact with the wall of the cylinder on a circumferential line of contact and diverging from said cylinder wall on opposite sides of said line of Contact, a sleeve slidable upon said piston rod, a" seccndary vpiston mounted to abut Y said main piston'and having a rocking engagement with said sleeve and extending longitudinally aboutr said Vsleeve and' within said' main pis.- ton' and thence outwardlyto contact with the wall of said cylinder on a circumferential line of con.- tact and diverging from,V said cylinder wall on opposite sides of said line of', contact, stopping means to limit the stroke ofthesecondary piston and sleeve, said rod having a passage communicatingvwith the space betweensaid pistons,.said cylinder having, communicating passages toits opposite ends on opposite: sides of said pair of cylinders. Y y

7.V The actuator of claim 6 in which the surfaces of said `pistons in contactf'with said ,cylinder walls vare of arcuate'curvature inllqngitudinal section.

8. The actuator of claim,6"in which said stop is mounted on said'v sleeve' and,` in which said cylinder is recessed to receive said, stop.

HENRY WILL-mM TRE'vAsKIs.

REFERENCES" CITED The following references are of record inthe le of this patent:

UNITED s'rzrresV i'irrnirrsy 219,471 Switzerland May. 1942 

